Switching devices for hydraulic pumps and motors



Filed Aug. 4. 1960 June 18, 1963 A. BR EDER 3,094,078

SWITCHING DEVICES FOR HYDRAULIC PUMPS AND MOTORS 2 Sheets-Sheet 1 v- 4 i2 l P3 8P HP r 1 8 Fig.2

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i I /I// iunm-on' Murmur Bnvtpm 22 Y ZL'AI'M n 1963 A. BRUEDER 3,094,078

swrrcamc DEVICES FOR HYDRAULIC PUMPS AND MOTORS Filed Aug. 4, 196 2sheets-Sheet 2 United States Patent ""ce 3,094,078 SWITCHING DEVICES FORHYDRAULIC PUMPS AND MOTORS Antoine Brueder, Paris, France, assignor toSociete Anonyme Andre Citroen, Paris, France, a corporation of FranceFiled Aug. 4, 1960, Ser. No. 46,740

Claims priority, application France Aug. 21, 1959 6 Claims. (Cl.103-162) The present invention relates to a device for switchinghydraulic pumps and motors and more generally to the application ofresonators to the switching of hydraulic pumps and motors.

The difficulty of switching hydraulic pumps and motors of thedistributor type, notably for relatively high pressures, is well knownto those conversant with the art. Many means have already been proposedwith a view to obtain a noiseless operation and a higher efiiciency.Thus, some known propositions are based on the shifting of thedistributor, or the provision of valve feed systems with or without anauxiliary source of fluid.

Interesting results are provided by these methods under well-definedoutput, pressure and rating conditions.

But in certain application such as hydraulic transmissions, theseparameters are particularly variable, and their rate of variation issometimes relatively high; moreover, the change in the direction ofrotation and the fact that the high-pressure side acts as a brake makethis switching problem more complicated and the difiiculty of applyingthe means set forth hereinabove is increased in proportion.

It is the essential object of this invention to provide a satisfactorysolution to this problem with due consideration for the variousparameters involved, by using a readily adjustable static systemcharacterized by a short response time. It consists essentially inconnecting each separating or overlapping surface of the distributorassociated with a hydraulic motor or pump with a resonator- :Eormin gcavity, so that the latter be energized by the pump or motor pressureand becomes operative to permit a gradual pressure connection in thedead space or cylinder capacity during the overlapping.

The invention will now be described with reference to the accompanyingdrawings illustnating diagrammatically by way of example a typical formof embodiment applicable to any similar or other types of slide-valvepumps and distributors. In the drawings:

FIGURE 1 is a fragmentary developed section showing a conventionalaxial-pump distributor provided with a resonator according to thisinvention;

FIGURE 2 is a -diagram plotting the pressure as a function of time inthe resonator of FIG. 1, the upper portion of this figure showingdiagrammatically the relative position of a cylinder with respect to thedistributor for each cycle of operation;

FIGURE 3 is a diagrammatic view showing a device according to thisinvention for adjusting the resonator;

:FIGURE 4 is a developed fragmentary section showing the distributor ofFIG. 1 with a resonator of the vortex yp FIGURE 5 is a vertical sectionshowing a modified form of embodiment of the invention;

FIGURE 6 is a section taken upon the line Vl-VI of FIG. 5, and

FIGURE 7 is a cross-section taken upon the line VII-VII of FIG. 6.

In FIG. 1 there is shown in fragmentary section a developed view of adistributor 1 of a conventional axial pump 2 comprising cylinders 6 inwhich pistons 4 are slidably mounted. The pump rotation causes thecylinders to communicate by turns with the liquid input and output mani-3,094,078 Patented June 18, 1963 2. holds 5, 6 respectively, thedistributor comprising so-called overlapping separating surfaces 7between the manifolds, these surfaces being coincident with the passagesof the pistons 4 at their top and bottom dead centres.

According to the present invention, there is provided a closed chamber 8communicating through a duct 8 with the distributor, this duct openingon the separating surface.

Thus, during the overlapping period the cylinder capacity or the deadspace, according as the piston is at its bottom dead centre or at itstop dead centre, communicates only with the chamber 8 and thecorresponding duct 8 acting as a resonator.

The dimensions of the overlapping surfaces and of the heads of theslide-forming cylinders 3 are so calculated that the resonator formed bythe chamber 8 and duct 8 be energized by the pressure of the hydraulicpump or motor, and becomes the seat of a periodic pressure variation ofwhich FIG. 2 represents the curve as a function of time; this functionis periodic and its period is wherein n is the number of cylinder of thepump or motor, and w the angular speed. Considering more particularlythe resonator corresponding to the passage of the piston shown in FIG. 1at the bottom dead centre in the time interval '9 (FIG. 2), theresonator will communicate with the high-pressure manifold HP; in thetime interval 10, with the cylinder 3 alone; in the time interval 11,with the low-pressure maniiold B-P, the resonator being isolated at 12This periodic energiza-tion produces in the resonator an alternatingoutput which, by being adequately phaseshifited with respect to thepressure by a suitable selection of the resonator characteristics,permits of properly efiecting the connection in the dead space of thecylinder or in the cylinder during the overlapping between the inductioncycle and the exhaust cycle at the dead centre passage (according as itis the bottom or top dead centre).

The output amplitude and phase-displacement depend on the impedance Z ofthe resonator of which the inertance is Z p F and the capacitancewherein p is the specific mass of the liquid,

1 is the length of duct 8 (FIG. 1) a s is the cnoss-secn'onal area ofthis duct (FIG. 1) V is the volume of chamber 8 (FIG. 1)

K is the module of compressibility of the liquid To this a resistanceterm due to the loss of pressure in the duct 8 and to the loss of speedat the outlet end of this duct must be added.

The geometrical dimensions of the duct and chamber provide the desiredimpedance Z.

The rear phase displacement which had to be will be only very closethereto due to the resistance term. The energy absorbed for thistransfer will be very moderate for the output will be practicallyreactive in comparison with the Wattless current of the electricalsystems.

In FIG. 3 there is shown by way of example a device for adjusting theresonator.

The length of duct 14 is variable through the displacement of theU-shaped pipe element 15 controlled at 16 either from the regulationsystem or manually. The volume 1 of the chamber varies as the piston 17is moved up or down in its cylinder, the piston rod 18 being alsocontrolled either by the regulating system or manually. The regulationsystem will be subordinate to the rate of operation and possibly of thepressure and volume (cylinder capacity or dead space) to be subjected tothe pressure connection.

By using a vortex resonator (FIG. 4) the desired impedance Z may beobtained without varying the capacitance, but in this case only theinertance is acted upon.

This adjustable resonator consists of a chamber 20 (in this case acircular chamber) communicating With a pivoting choke 19.

With this arrangement, the inertance of the duct 21 is completed by thecariable inertance of the vortex created by the tangential component ofthe input or output speed of choke 19. This tangential component is afunction of the angle of setting of the choke. The angular displacementis controlled by means of a lever 22 responsive to the regulation systemor to manual adjustment means.

This resonator may be used for the two dead centres mainly in pumps ormotors having an odd number of cylinders.

FIGURES 4 and illustrate this application and the alternate positions ofducts 21' with respect to the cylinders may be clearly seen therein.

Thus, when at the bottom dead centre 23 the cylinder communicates withthe resonator, the communication is shut off at the top dead centre 24,and vice versa. If reference is made to the diagram of FIG. 2 to explainthe energization of the resonator, it will be seen that in position 9the resonator communicates with the high-pressure manifold 26 throughthe two dead centres 23 and 24; at 10, the cylinder in the bottom deadcentre position communicates with the resonator of which the top deadcentre orifice is closed; at 11, the resonator communicates with thelow-pressure manifold through the tWo dead centres 23 and 24, at 12 thecylinder passing through the dead centre 24 communicates with theresonator of which the orifice of dead centre 23 is closed. Therefore,the function of the resonator is to transfer with a very good efficiencythe expansion energy from one cylinder in the form of recompressionenergy into the other cylinder.

However, the excitation would not be symmetrical, notably for themaximum volumetric adjustment of the pump or motor, for the cylinderspassing through the dead centres 23 and 24 have a different cubiccapacity. To restore the symmetry, a complementary volume correspondingto the cylinder capacity defined by the volumetric adjustment must beadded to the cylinder in the dead centre position.

In FIG. 5 there is shown by way of example in the specific case of anaxial pump or receiver, provided with a distributor 27 receiving themanifolds BP (low-pressure) 28 and HP (high-pressure) 29, a devicemeeting this requirement. The assembly comprises the vortex resonator 30communicating through a duct 31 with the overlapping surfaces and ateach dead centre there is an adjustable volume consisting of a cylinder32 or 33, provided with a piston 34 or 35, actuatable by means of itsrod 36 or 37.

The resonator 30 will communicate simultaneously with the cylinder 38passing through a dead centre position and with the correspondingauxiliary volume as shown in FIG. 5. The piston 34 will reduce thevolume of the cylinder to a minimum for it communicates with thecylinders passing through the bottom dead centre, Whilst the piston 35Will give to the cylinder 39 the volume corresponding to the cubiccapacity of a piston. The displacement of piston 35 will be adjusted asa function of the volumetric adjustment of the pump or receiver which iseffected by inclining a plate or disc 40 by means of a lever 41 in thisspecific example. For negative inclinations of the plate or disc 40 thefunctions of the cylinders 32 and 33 will be reversed.

This device suitable for a practical application is efficient andreliable in operation. Moreover, it is characterized by the advantageousfeature of being applicable to the switching of hydraulic pumps andmotors operating under extremely variable speed conditions.

I claim:

1. In a hydraulic machine operating as a generator or a receiver of thetype comprising a rotating barrel fixed on a shaft, spaced cylindersprovided in said barrel, a piston in each cylinder, and a distributorhaving high and low pressure manifolds cooperating with the cylinders,and connecting surfaces between said high and low pressure manifolds,the combination with a resonator and a duct connecting said resonatorwith said connecting surfaces to permit a gradual connection of thepressure with said cylinders, and means for regulating the frequency atwhich the resonator is resonant.

2. A device as set forth in claim 1 wherein the length of the duct isadjustable.

3. A device as set forth in claim 1, wherein the resonator comprises apivoting choke communicating with the duct and means for manualadjustment of this choke.

4. A device as set forth in claim 1, wherein a resonator is connected toeach connecting surfaces.

5. A device as set forth in claim 1, wherein a complementary volume isconnected by a duct with each of said connecting surfaces.

6. A device as set forth in claim 5, wherein means are provided toadjust the volume of the complementary volume.

References Cited in the file of this patent UNITED STATES PATENTS1,624,363 Rey Apr. 12, 1927 2,225,398 Hamblin Dec. 17, 1940 2,252,256Harris Aug. 12, 1941 2,474,512 Bechtold June 22, 1949 2,642,809 Born etal June 23, 1953 2,804,828 Grad Sept. 3, 1957 2,847,938 Gondek Aug. 19,1958 2,855,857 Chien-Bor Sung Oct. 14, 1958

1. IN A HYDRAULIC MACHINE OPERATING AS A GENERATOR OR A RECEIVER OF THE TYPE COMPRISING A ROTATING BARREL FIXED ON A SHAFT, SPACED CYLINDERS PROVIDED IN SAID BARREL, A PISTON IN EACH CYLINDER, AND A DISTRIBUTOR HAVING HIGH AND LOW PRESSURE MANIFOLDS COOPERATING WITH THE CYLINDERS, AND CONNECTING SURFACES BETWEEN SAID HIGH AND LOW PRESSURE MANIFOLDS, THE COMBINATION WITH A RESONATOR AND A DUCT CONNECTING SAID RESOANTOR WITH SAID CONNECTING SURFACES TO PERMIT A GRADUAL CONNECTION OF THE PRESSURE WITH SAID CYLINDERS, AND MEANS FOR REGULATING THE FREQUENCY AT WHICH THE RESONATOR IS RESONANT. 